This invention relates to the field of cutting apparatuses for large-area material in sheet form, and particularly for photo-printing paper in strips. A cutting apparatus for exposed and developed photo-printing paper which cuts the edges of a sheet of paper laid on a processing table is available. The cutter head of this apparatus consists of a roller cutter mounted in a holding device which moves along a guide bar and interacts with a stationary linear cutter to produce a cut. The holding device is fastened to a chain which runs over reversing pulleys on the side plates of the cutting table. A pinion of an electric motor can be connected to the two sides of the chain so that cuts are alternatively made from the two sides of the cutting table in succession.
This invention is related to this apparatus for exposed photo-printing paper, but is primarily intended to solve a different cutting problem, the problem of cutting unexposed photo-printing paper. In photo-printing machines in which the unexposed photo-printing paper is drawn off a delivery spool and cut off in accordance with the length of the original, the cut must be made when the rear of the original has reached the processing table, and a sufficient quantity of photo-printing paper, usually guided from a delivery spool mounted underneath the entry table around the rounded front edge of the table, has been drawn off.
Unless the photo-printing machine is fitted with an automatic cutting device, which makes the cut automatically in accordance with the scanned end of the original, the cutting has to be done by hand. For this purpose systems are known in which a thin wire is placed in a groove located approximately along the top line of the rounded front edge of the processing table. The wire is fixed on one side of the table while being attached to a spring on the other side. The wire runs through a ring with which it can be pulled out of the groove against the force of the spring. In rest this ring occupies a position adjacent to the photo-printing paper being guided over the front edge of the feed table. To cut off the paper the ring is gripped and drawn across the feed table, so that the wire emerges from the groove and cuts through the photo-printing paper stretched across the table.
A cutting apparatus of this kind cannot be mechanized, and its manual operation has a number of drawbacks, of which the most serious is slowness. The slower the ring is moved across the table, the more oblique will be the cut made in the photo-printing paper, which, of course, is moving while being cut.
A cutting apparatus operating to some extent in the reverse manner also has been designed. This apparatus has a wire stretched above the processing table, and a groove provided in the table. The wire is drawn downwards into the groove by a motor, thereby cutting the paper. This system however, suffers from the serious drawback that if the cutting apparatus is actuated too soon the photo-printing paper will be cut too short. In addition the original, which is situated above the photo-printing paper and therefore between the processing table and the cutting wire, also will be cut and irreparably damaged.